1. Field of the Invention
The present invention generally relates to an oil activated fuel injector. More particularly, the present invention relates to a rail connection with rate shaping behavior for an oil activated electronically or mechanically controlled fuel injector.
2. Background Description
There are many types of fuel injectors designed to inject fuel into a combustion chamber of an engine. For example, fuel injectors may be mechanically, electrically or hydraulically controlled in order to inject fuel into the combustion chamber of the engine. In the hydraulically actuated systems, a control valve body may be provided with two, three or four way valve systems, each having grooves or orifices which allow fluid communication between working ports, high pressure ports and venting ports of the control valve body of the fuel injector and the inlet area. The working fluid is typically engine oil or another type of suitable hydraulic fluid that is provided to the fuel injector via a rail connection system. The working fluid, once provided to the fuel injector, is capable of providing a pressure within the fuel injector in order to begin the process of injecting fuel into the combustion chamber.
However, in current connection rail designs, a large amount of working fluid is initially permitted to flow into the inlet area of the fuel injector. This large volume of initial working fluid causes bouncing effects of the injector valve of the fuel injector. Also, a small quantity (pilot injection) of fuel cannot be efficiently injected into the engine during a pre-stroke phase of the plunger due to the fact that a large quantity of working fluid is initially allowed to flow into the inlet area of the fuel injector. These shortcomings lead to higher emissions and engine noise.
In presently known designs, to provide a smaller quantity of fuel to the combustion chamber of the engine a delay of the pre-stroke of the plunger must be provided. However, this can only be provided in the conventional system by adding more working fluid, under high pressure, into the injector. The additional pressurized working fluid may cause a delay; however, additional energy from the high pressure oil pump must be expanded in order to provide this additional working fluid. This leads to an inefficiency in the operations of the fuel injector itself, and also does not provide a consistent supply of fuel into the engine.
The present invention is directed to overcoming one or more of the problems as set forth above.
It is an object of the present invention to provide a fuel injector with improved efficiency.
It is another object of the present invention to provide a rail connector assembly that provides a pilot injection of fuel without the need to expend additional energy at the oil pump.
It is still another object of the present invention to provide a fuel injector that minimizes a bounce effect of a control body.
According to one aspect of the invention, a rail connection assembly generally includes an outer rail connection tube having a rail connection outlet and a component having a substantially centrally located bore, said component being fixed to said outer rail connection tube remote from said rail connection outlet. A piston adapted for movement between a first position and a second position, with the second position being remote from the bore, is also provided. A nipple with a predetermined cross-section extends from the piston and is slidably movable into and remote from the bore as the piston is moved between the first and second positions. A fluid communication path exists between the bore and the rail connection outlet.
In embodiments, a plurality of lateral grooves are formed in either the component or the outer rail connection tube to provide the fluid communication path between the bore and the rail connection outlet. An annular groove may also be formed in either the component or the outer rail connection tube to provide fluid communication between the bore and the rail connection outlet. The piston may also include a bore disposed proximate said nipple for providing a further fluid communication path. A spring disposed within the piston and resting on a spring seat, which may be provided either on the piston or the outer rail connection tube, tends to bias the piston towards the first position, and therefore provides a restoration force when the piston is moved into the second position.
According to another aspect of the invention, a pressurized working fluid is allowed to flow into the rail connection assembly. This tends to bias the piston downwards, opening a gap within the rail connection assembly. The first amount of working fluid passes through the gap and into an inlet on a fuel injector, thereby triggering a pilot injection of fuel. As additional working fluid is introduced, the piston is fully biased into the second position, which opens a larger second gap. A full amount of working fluid is then allowed to pass into the inlet triggering a main injection.